JP2023168473A - High-frequency plasma cvd apparatus - Google Patents

Abstract

To provide an ultra-high-frequency plasma CVD apparatus including a radiation heating and thermoelectron generating electrode to solve such the problem that a carbon-based thin film material such as diamond and graphene draws attention as a new semiconductor material for creating a new electronic device and a microwave plasma method, a thermal filament method and the like have been developed as the method for manufacturing the same, however, the former has a problem with suppression of ion damage and the latter has a problem with increase in film deposition rate.SOLUTION: A high-frequency plasma CVD apparatus includes: a radiation heating and thermoelectron generating electrode for heating a substrate with radiation and generating a thermoelectron; and a high-frequency plasma generating electrode including a quartz window and a raw material gas jetting hole having a high opening ratio with 0.2-1 mm diameter. The high-frequency plasma CVD apparatus measures and controls temperatures of the substrate and the radiation heating and thermoelectron generating electrode via the high-frequency plasma generating electrode using a radiation thermometer and converts a carbon-containing raw material gas into plasma to form a carbon-based thin film such as diamond and graphene.SELECTED DRAWING: Figure 1

Description

The present invention relates to a high frequency plasma CVD apparatus. In particular, the present invention relates to a high frequency plasma CVD apparatus for forming a carbon-based thin film using a thermionic generation electrode that also serves as radiation heating and a high frequency plasma generation electrode in the VHF band (30 MHz to 300 MHz).

In recent years, carbon-based thin films such as graphene and diamond have attracted attention.
Graphene is a crystal with a structure in which carbon atoms are bonded in a honeycomb shape on a two-dimensional plane without gaps and have an sp2 hybrid orbital. Graphene is a material that has excellent electrical, mechanical, and optical properties, and is thermally and chemically stable, so it is expected to be put to practical use in many industrial fields.
Methods for producing graphene have been proposed, including mechanical exfoliation, chemical vapor deposition (CVD), SiC pyrolysis, and plasma CVD, and research and development is currently underway with the aim of further development. ing. Among the above manufacturing methods, the plasma CVD method is the most promising method from the viewpoint of application of graphene to electronic devices. The plasma CVD method, for example, as described in Non-Patent Document 1 and Patent Document 1, involves turning a mixed gas of a carbon-containing gas such as CH ₄ or C ₂ H ₄ and hydrogen gas (H ₂ ) into plasma. This method has the advantage of being able to form graphene on a large-area substrate. However, as described in, for example, Non-Patent Document 1 and Patent Document 1, the plasma CVD method has high Quality graphene formation is difficult. That is, a graphene forming apparatus using the plasma CVD method has a difficult problem of suppressing ion damage.
One of the methods proposed to solve this problem is, for example, the method described in Patent Document 1. The graphene film forming method using microwaves described in Patent Document 1 involves generating microwave plasma on the surface of a substrate at a pressure of 1 Torr or more and a substrate temperature of 500° C. or less to form a graphene film having 1 to 2 layers. A method for forming a graphene film comprising: applying microwaves to the inside of the nozzle and/or to the edge or periphery of the nozzle while blowing a raw material gas containing a carbon-based gas onto the surface of the base material from a nozzle; The method includes a step of generating plasma containing radicals from a raw material gas, and controlling the flow rate of the raw material gas to forcefully diffuse the radicals onto the surface of the base material, regardless of the processing time of the step. It is characterized in that it is produced under growth conditions that stop self-growth, where growth stops when the number of layers is 1 to 2.
However, in the method described in Patent Document 1, since the microwave propagation line has an elongated slit shape, plasma is generated in an elongated slit shape. As a result, it has the disadvantage that its application is limited to graphene formation by a roll-to-roll method that takes advantage of the characteristics of elongated slit-shaped plasma.

Diamond is known as a wide-gap semiconductor, as described in, for example, Non-Patent Document 2, Non-Patent Document 3, and Patent Document 2, and has far superior properties to semiconductors such as Si and SiC. , is attracting attention as the ultimate power semiconductor material. In order to apply this technology to power semiconductor materials, research and development are being carried out on large-area diamond forming apparatuses and methods that can be applied to 4- to 5-inch substrates.
It is known that there are two main methods for forming diamond as a power semiconductor material: microwave plasma CVD and hot filament CVD. Additionally, the following is generally known: That is, in the CVD method, when diamond is used for the substrate, diamond is formed by homoepitaxial growth, impurities can be easily controlled, and a strain-free crystal can be formed. Further, when the substrate is made of a material other than diamond, diamond is formed by heteroepitaxial growth, which may cause distortion and reduce crystallinity.

The microwave plasma CVD method used for diamond formation is characterized by using microwaves to heat the substrate and decompose raw material gas, as described in Patent Document 2, for example. In other words, by using microwaves to turn a mixed gas of methane (CH ₄ ) and hydrogen (H ₂ ), which are raw material gases, into plasma, the electrons and ions generated in the plasma are essential for forming a diamond film. In addition to generating CH ₃ radicals and atomic hydrogen H, which are the main radicals of Heat. Diamond formed on a substrate uses CH ₃ radicals or the like as a main precursor, which is chemically adsorbed onto the substrate, and hydrogen components and graphite components are removed by atomic H or the like on the substrate, and diamond crystals grow.
The diamond forming apparatus described in Patent Document 2 is a CVD apparatus for diamond synthesis that forms a diamond film on the surface of a substrate, and includes an upper hemispherical surface having a flat dome shape and a lower hemispherical surface having a flat dome shape. a coaxial antenna member that extends along the central axis of the discharge chamber through the lower hemispherical surface and supplies microwaves to the inside of the discharge chamber; A disc-shaped resonant antenna is installed indoors at the tip of the coaxial antenna member and extends concentrically with the central axis along the maximum diameter surface of the discharge chamber, and a disc-shaped resonant antenna having a circular outer periphery and attached to the upper surface of the resonant antenna. The device is characterized by comprising a mounting table on which the substrate is placed, which is arranged concentrically with the center axis at the center of the substrate.
However, from the viewpoint of application to the formation of the power semiconductor material of diamond, the microwave plasma CVD method is generally Although the diamond growth rate is relatively high at 1 to 10 μm/h, the width of the uniform plasma generation area is limited due to the short wavelength of microwaves, and the area that can be deposited is λ/8 to λ/10. The problem is that it is difficult to increase the area, which is an essential condition for dealing with 4- to 5-inch substrates. In the case of a frequency of 2.45 GHz, the wavelength λ in high-density plasma is the wavelength λ ₀ (122 mm) in vacuum x wavelength shortening rate (for example, 0.65) = 79.3 mm, and a uniform high-density plasma generation region If it is estimated to be, for example, about λ/8 to λ/10, the area where a film can be formed is about 8 to 10 mm in diameter.
In addition, in microwave plasma, surface wave plasma using a quartz window is applicable to large-area substrates, because the surface wave plasma etches the quartz window and releases oxygen atoms and silicon atoms. It is known that it is unsuitable for application to electronic devices that avoid contamination with impurities such as atoms.

The hot filament CVD method is characterized by using radiant heat to heat the substrate, and by using hot electrons, ultraviolet rays, etc. emitted from the hot filament to decompose the source gas. That is, a high-temperature filament (approximately 1,000°C to 2,400°C) is installed at a position several mm to 10 mm directly above the substrate, and source gas is heated by thermionic and ultraviolet rays emitted from the high-temperature filament. A certain mixed gas of hydrogen (H ₂ ) and methane (CH ₄ ) is decomposed to generate CH ₃ radicals, etc., which are the main radicals essential for forming a diamond film, and atomic hydrogen H, etc. Diamond uses CH ₃ radicals and the like as a main precursor, and while being chemically adsorbed onto a substrate, hydrogen components and graphite components are removed by atomic H and the like on the substrate, and diamond crystals are formed. The temperature of the substrate is generally set at about 700 to about 1,000°C.
However, from the viewpoint of application to the formation of the ultimate power semiconductor material, the hot filament CVD method generally has a film formation rate of 1 Since the speed is as low as .5 to 2.0 μm/h, the challenge is to realize high-speed film formation on the same level as microwave plasma CVD. In addition, in order to apply it to power semiconductor materials, it is necessary to increase the area so that it can be applied to 4- to 5-inch substrates.

An example of a typical patented technology regarding a diamond forming apparatus using hot filament CVD is Patent Document 3.
Patent Document 3 includes the following description regarding a diamond forming apparatus using a hot filament method.
In other words, hot filament CVD is a film forming method in which a raw material gas supplied to a film forming chamber is thermally decomposed using a high temperature filament to induce a chemical reaction, and it has a simple structure and is inexpensive, and also allows for a large film forming area. be able to. However, conventional hot filament CVD has a problem in that the growth rate of film formation is lower than that of plasma CVD.
As a hot filament CVD apparatus that solves this problem, the apparatus described in Patent Document 3 includes a film forming chamber, a substrate holder placed in the film forming chamber for placing a substrate, and a temperature of 2,500° C. or higher. The filament layer is provided with a filament layer to be heated, a gas supply means for supplying a source gas and a carrier gas into the film forming chamber, and an exhaust means for exhausting gas from the film forming chamber, and the filament layer is The filament layers are arranged in multiple stages at intervals of 1 to 10 mm, and each of the filament layers arranged in the multiple stages includes wires made of tantalum or its alloy with a wire diameter of 0.1 to 1.0 mm at intervals of 3 to 30 mm. It is characterized by having multiple pieces arranged.
Further, the hot filament CVD apparatus described in Patent Document 3 uses tantalum (Ta) as the material of the hot filament as a means to increase the amount of thermionic generation (thermionic emission amount), and the temperature of the hot filament is set to 2. , 500° C. or higher, and the hot filaments are arranged in multiple stages.
An example of a hot filament CVD apparatus described in Patent Document 3 includes the following description.
(1) The diameter of the filament is in the range of 0.1 to 1.0 mm, preferably in the range of 0.1 to 0.3 mm.
(2) The spacing between filaments forming one filament layer is in the range of 3 to 30 mm, preferably 5 to 15 mm.
(3) The distance between the first filament layer and the second filament layer is in the range of 1 mm to 10 cm, preferably 1 to 10 mm.
(4) Various materials can be used for the filament as long as it can withstand high temperatures of 2,400° C. or higher. For example, they are tungsten, tantalum, etc., and these may be alloys thereof or compounds such as carbides. Tantalum is preferred.

On the other hand, as seen in Patent Document 4 and Patent Document 5, for example, a diamond forming apparatus using VHF plasma CVD in which the frequency of the power source is in the VHF band (30 to 300 MHz) has been proposed.
The VHF plasma CVD diamond forming apparatus described in Patent Document 4 is characterized in that it uses power in the ultrahigh frequency range (30 to 300 MHz) when synthesizing diamond by the plasma CVD method that uses plasma for opposed electrode capacitive discharge. do.
The VHF plasma CVD diamond forming apparatus described in Patent Document 5 uses an inductively coupled plasma CVD method and a high frequency frequency of 40 to 250 MHz to form a diamond film using a carbon-containing raw material. It is characterized by decomposing gas and forming a diamond film on the substrate.
However, a VHF plasma CVD diamond forming apparatus that can control the substrate temperature to about 700 to about 1,000° C., suppress ion damage, and form high-quality diamond has not yet been developed.

Patent 6661189 Patent 7304280 Patent 7012304 Tokuho 07-042197 JP 08-027576

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As described above, in forming graphene by the plasma CVD method, it is a problem to eliminate irradiation damage due to ion bombardment. As a method for solving this problem, for example, a method described in Patent Document 1 has been proposed. However, the method described in Patent Document 1 has a disadvantage in that, because the plasma generation region is in the form of an elongated slit, its application is limited to graphene formation by a roll-to-roll method.
In the microwave plasma CVD method for diamond formation, for example, the method described in Patent Document 2 uses a short microwave wavelength, so the plasma generation area is small (for example, 2.45 GHz). The problem is that it is essentially difficult to handle substrates of 4 to 5 inches in size.
The hot filament CVD method for diamond formation is, for example, the diamond forming method using the hot filament CVD method described in Patent Document 3, which is suitable for generating a large amount of CH ₃ radicals etc. and atomic H etc. at the hot filament temperature during diamond formation. The substrate temperature is set at approximately 2,400 to approximately 2,500°C or higher (herein referred to as device operating parameter A), and the substrate temperature is set to approximately 700 to approximately 1,000°C, which is suitable for diamond growth (herein referred to as device operating parameter A). , device operation parameter B) has the following problems.
The generation of thermionic electrons follows the Richardson-Dushman formula (the generation of thermionic electrons is proportional to the square of the hot filament temperature), for example, as described in Non-Patent Document 4. When generating a large amount of thermoelectrons, the higher the temperature of the hot filament, the better. On the other hand, when the temperature of the hot filament is increased, the radiant energy of the hot filament reaching the substrate increases by 4 times the temperature of the hot filament according to the Stefan-Boltzmann law, as described in Non-Patent Document 5, for example. Since it is proportional to the square of the distance between the hot filament and the substrate, if the temperature of the hot filament is increased, the temperature of the substrate will rise.
That is, for example, in the diamond forming method using the hot filament CVD method described in Patent Document 3, the temperature of the hot filament is raised to generate a large amount of thermoelectrons (device operating parameter A), and the substrate temperature is set to an appropriate value (device There is a relationship (trade-off relationship) in which the operating parameters B) are incompatible. Therefore, the device operating parameter A, which is an increase in the amount of thermionic and ultraviolet rays (higher density of thermionic electrons) that have the effect of generating a large amount of CH ₃ radicals and atomic H, which are essential for diamond formation, and the diamond growth It is difficult to achieve both device operation parameter B, which is the setting of an appropriate value for the substrate temperature, which is essential for this purpose. As a result, there is a problem in that it is difficult to increase the diamond film formation rate (growth rate).
In the VHF plasma CVD method using the VHF band (30 MHz to 300 MHz) as the power supply frequency, for example, as described in Non-Patent Document 6, the plasma sheath voltage (the difference between the plasma potential V _p and the wall potential V ₄ : V _p -V ₄ ) is low, and ion damage is suppressed. Furthermore, for example, as described in Non-Patent Document 7, it is possible to generate a high concentration of atomic hydrogen H, and the concentration of the atomic hydrogen H increases in proportion to the pressure. It has characteristics. That is, the VHF plasma CVD method is characterized in that it is possible to suppress ion damage and to generate high concentration atomic H, and is expected to be applied to diamond forming apparatuses.
However, there are no conventional diamond forming methods using VHF plasma CVD other than the methods described in Patent Documents 4 and 5, and the substrate temperature can be controlled at about 700 to about 1,000 degrees Celsius, ion damage is suppressed, A VHF plasma CVD diamond forming apparatus capable of forming high quality diamond has not yet been developed.
In the VHF plasma CVD method, the wavelength of the generated plasma is sufficiently longer than that of microwave plasma, so there is no problem caused by the wavelength. Therefore, the challenge is to create a method for forming diamond by VHF plasma CVD that can be put to practical use.
An object of the present invention is to provide an apparatus for forming carbon-based films such as diamond and graphene by high-frequency plasma CVD, which can solve the above-mentioned problems. That is, the object of the present invention is to provide a high-frequency plasma CVD apparatus for forming a carbon-based thin film that is capable of high-speed film formation and can be applied to large-area substrates in the 4- to 5-inch class. Another object of the present invention is to provide a high-frequency plasma CVD apparatus that can suppress ion damage and can generate CH ₃ radicals, C ₂ H ₃ radicals, etc., and highly concentrated atomic H, etc.

A first aspect of the present invention for solving the above-mentioned problems is to provide a reaction vessel equipped with a supply system and an exhaust system for a raw material gas containing at least carbon-containing gas and hydrogen gas (H ₂ ), and an interior of the reaction vessel. a substrate holding stand having a main surface for holding a substrate and having a substrate cooling means using a refrigerant to control the temperature of the substrate; and a substrate holding stand disposed opposite to the main surface of the substrate holding stand. a radiant heating and thermionic generation electrode that generates radiant heat and thermionic electrons; a DC power source that supplies DC power to the radiant heating and thermionic generation electrode; A high-frequency plasma CVD apparatus comprising: a high-frequency plasma generating electrode that converts the raw material gas into plasma; and a high-frequency power source that supplies high-frequency power to the high-frequency plasma generating electrode via an impedance matching device.
The heat generating part of the thermionic generation electrode that also serves as radiation heating is formed of tungsten, tantalum, or an alloy containing tantalum, which is a material with a low work function φ,
The high frequency power supply generates power at a frequency selected from the VHF band (30MHz to 300MHz),
The high-frequency plasma generation electrode is formed into a box shape having a cavity inside using a metal material, and the box-shaped high frequency plasma generation electrode is fixed to the wall of the reaction container by penetrating through an electrical insulating material. A surface of the box-shaped high-frequency plasma generation electrode that does not face the radiant heating/thermionic generation electrode is provided with a power feeding point to which the power of the high-frequency power supply is supplied and an inlet for the raw material gas, and the box-shaped high-frequency plasma is generated. A quartz window that transmits infrared rays is arranged on the surface of the generation electrode in contact with the atmosphere, and a quartz window with a diameter of 0.3 mm to 1.0 mm is disposed on the surface of the box-shaped high frequency plasma generation electrode facing the radiant heating and thermionic generation electrode. A large number of injection holes for the raw material gas with an aperture ratio of 30% to 90% are arranged, and the radiation thermometer placed outside the reaction vessel is used to measure the temperature of the raw material gas through the quartz window and the injection holes for the raw material gas. The method is characterized in that the temperature of the substrate and the temperature of the thermionic generation electrode that also serves as radiation heating are measured.
In a second invention, in the first invention, the carbon-containing gas is methane (CH ₄ ), ethane (C ₂ H ₆ ), propane (C ₃ H ₈ ), ethylene (C ₂ H ₄ ), propylene ( It is characterized by being a gas containing at least one selected from C ₃ H ₆ ) and acetylene (C ₂ H ₂ ).

As described above, the high-frequency plasma CVD apparatus of the present invention generates radiant energy that heats the substrate and thermoelectrons that dissociate the source gas and generate CH ₃ radicals, C ₂ H ₃ radicals, etc., and high concentration atomic H, etc. A thermionic generation electrode that can be used for both radiation heating and ultra-high frequency plasma generation with suppressed ion damage that turns the raw material gas into plasma and generates CH ₃ radicals, C ₂ H ₃ radicals, etc., and high concentration atomic H, etc. The high-frequency plasma generating electrode has a box-shaped structure, and a quartz window disposed on the box-shaped high-frequency plasma generating electrode has a diameter of 0.3 mm to 1.0 mm and an aperture ratio. The temperature of the substrate and the temperature of the thermionic generation electrode that also serves as radiation heating are measured through the ejection hole of the raw material gas, which is 30% to 90%, with a radiation thermometer placed outside the reaction vessel, and the temperature of the substrate is measured. Moreover, there is an effect that the temperature of the thermionic generation electrode for both radiation heating and heating can be stably controlled. Further, the action and effect of dissociating the raw material gas of the thermionic electrons emitted from the radiation heating and thermionic generation electrode are the same as the action and effect of dissociating the raw material gas of the VHF plasma generated by the high frequency plasma generation electrode. It has the effect of creating a synergistic effect.
That is, the high-frequency plasma of the raw material gas generated by the high-frequency plasma generation electrode inherently has α action (the action in which electrons collide with gas molecules and ionize them to generate new electrons) and β action (the action in which ions collide with gas molecules to generate new electrons). In addition to the ionization and dissociation of the raw material gas due to the action of colliding with the thermoelectron and generating electrons, the raw material gas is ionized and dissociated due to the action of the thermionic electrons emitted from the radiation heating and thermionic generation electrode. This has the effect of making it possible.
As a result, ion damage can be suppressed, and due to the synergistic effect of the thermionic action and the ultra-high frequency plasma action, precursors of carbon-based thin films such as high concentration CH ₃ radicals and C ₂ H ₃ radicals and high concentration It becomes possible to generate atomic H, etc., and it becomes possible to grow and form carbon-based thin films such as diamond and graphene over a large area and with high quality. In other words, the above problem can be solved.

FIG. 1 is a schematic cross-sectional view showing the configuration of a high-frequency plasma CVD apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic configuration diagram showing the configuration of a first radiation heating/thermionic generation electrode which is a component of the high frequency plasma CVD apparatus according to the first embodiment of the present invention. FIG. 3 shows radiant energy and thermoelectrons emitted from a first radiation heating and thermoelectron generating electrode, which is a component of a high frequency plasma CVD apparatus according to a first embodiment of the present invention, and a high frequency plasma generating electrode and a substrate. FIG. 3 is a schematic diagram illustrating the principle of plasma generated between holding tables. FIG. 4 is a schematic diagram showing the principle of decomposition of source gas (mixed gas of methane CH ₄ and hydrogen H ₂ ) by plasma in the high frequency plasma CVD apparatus according to the first embodiment of the present invention. FIG. 5 is a schematic diagram showing the principle of the growth process of diamond formed using the high-frequency plasma CVD apparatus according to the first embodiment of the present invention. FIG. 6 is a schematic configuration diagram showing the configuration of the second radiation heating/thermionic generation electrode 22 which is a component of the high frequency plasma CVD apparatus according to the second embodiment of the present invention. FIG. 7 is a schematic diagram showing the principle of the growth process of graphene formed using a high-frequency plasma CVD apparatus according to the second embodiment of the present invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In each figure, similar members are given the same reference numerals, and overlapping explanations will be omitted.
Note that the present invention is not limited to the following description, and can be modified as appropriate without departing from the gist of the present invention. Further, in the drawings shown below, for convenience of explanation, the scale of each member may be different from the actual scale. Furthermore, the scales of the drawings may differ from the actual scale.

The present invention relates to a high-frequency plasma CVD apparatus capable of forming carbon-based films such as diamond and graphene using plasma with suppressed ion damage.

(First embodiment)
First, the configuration of a high frequency plasma CVD apparatus according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 5. The following description will be made on the premise that the high-frequency plasma CVD apparatus of the present invention is applied to diamond formation, which is one of the application themes.
FIG. 1 is a schematic cross-sectional view showing the configuration of a high-frequency plasma CVD apparatus according to a first embodiment of the present invention.
FIG. 2 is a schematic configuration diagram showing the configuration of a first radiation heating/thermionic generation electrode which is a component of the high frequency plasma CVD apparatus according to the first embodiment of the present invention.
FIG. 3 shows radiant energy and thermoelectrons emitted from a first radiation heating and thermoelectron generating electrode, which is a component of a high frequency plasma CVD apparatus according to a first embodiment of the present invention, and a high frequency plasma generating electrode and a substrate. FIG. 4, which is a principle schematic diagram showing the plasma generated between the holding tables, shows the raw material gas (mixed gas of methane CH ₄ and hydrogen H ₂ ) in the high-frequency plasma CVD apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic diagram showing the principle of decomposition by plasma.
FIG. 5 is a schematic diagram showing the principle of the growth process of diamond formed using the high-frequency plasma CVD apparatus according to the first embodiment of the present invention.

As shown in FIGS. 1 and 2, the high-frequency plasma CVD apparatus according to the first embodiment of the present invention includes a supply system and an exhaust system for source gas containing at least carbon-containing gas and hydrogen gas (H ₂ ). a reaction vessel 1, a substrate holding stand 6 disposed inside the reaction vessel 1, having a main surface 6a for holding a substrate 9, and having a coolant for controlling the temperature of the substrate 9; A radiant heating and thermionic generation electrode 2 that is arranged to face the main surface 6a of the table 6 and generates radiant heat and thermionic electrons, and a DC power source 8 that supplies DC power to the radiant heating and thermionic generation electrode 2. , a high frequency plasma generating electrode 13 which is disposed opposite to the radiation heating and thermionic generating electrode 2 and converts the raw material gas into plasma, and high frequency power is supplied to the high frequency plasma generating electrode 13 via an impedance matching device 11. A high frequency power source 10 is provided. The DC power source 8 supplies DC power to the radiant heating and thermoelectron generating electrode 2 via a coil 16 that cuts off high frequency power and a first electrically ungrounded current introduction terminal 12a for the vacuum device. The high-frequency power supply 10 supplies high-frequency power to the high-frequency plasma generation electrode 13 via the impedance matching device 11 and the electrically ungrounded third vacuum device current introduction terminal 12c.
The reaction vessel 1 is a cylindrical box-shaped or rectangular box-shaped reaction vessel. Inside the reaction vessel 1, a high-frequency plasma generation electrode 13, a first radiation heating/thermionic generation electrode 2, and a substrate holding table 6 having a main surface 6a for holding a substrate 9 are arranged. As shown in FIG. 1, the radiation heating and thermionic generation electrode 2 is arranged to face the substrate holding table 6, and the high frequency plasma generation electrode 13 is arranged to face the radiant heating and thermionic generation electrode 2. will be placed.
The reaction vessel 1 is equipped with exhaust ports 17a and 17b connected to a vacuum pump (not shown). By operating the exhaust ports 17a and 17b in combination with a vacuum pump (not shown), it is possible to adjust the inside of the reaction vessel 1 to a predetermined pressure and maintain this pressure. Furthermore, it is possible to evacuate the inside of the reaction vessel 1 to a high degree of vacuum.
The reaction vessel 1 is equipped with a working flange (not shown) for assembling and arranging various components inside the reaction vessel 1.

The substrate holding stand 6 has a main surface 6a, and the main surface 6a contacts and holds the substrate 9. The substrate 9 is heated by the radiant heat emitted by the first radiation heating/thermionic generation electrode 2, and is heated to a predetermined temperature in cooperation with a substrate cooling means using a refrigerant (not shown) provided inside the substrate holding table 6. controlled. The temperature of the substrate 9 is set at about 700 to about 1,200°C, for example 1,000°C. Note that the temperature of the substrate 6 is measured using a radiation thermometer 19, which will be described later.
The cross-sectional shape of the substrate holder 6 is similar to the shape of the substrate 9. For example, when the size of the substrate 9 is a disk shape with a diameter of 5 inches, the size is one size larger, for example, 153 mm in diameter. For example, if the size of the substrate 9 is a rectangular plate measuring 5 inches x 5 inches, the size is one size larger, for example, 153 mm x 153 mm.
By opening and closing a substrate loading/unloading valve (not shown), the substrate 9 is loaded and placed on the main surface 6a of the substrate holding table 6 from the atmosphere side, and after the intended plasma processing is performed, it is carried out to the atmosphere side. be done.
Here, the substrate 9 is, for example, a single crystal Si wafer with a diameter of 5 inches. The size of the main surface 6a of the substrate holding table 6 is, for example, 153 mm in diameter. Note that the substrate 9 is not limited to a single-crystal Si wafer; for example, a plurality of small-sized diamond substrates manufactured by a high-temperature, high-pressure method may be placed thereon.

As shown in FIG. 2, the first radiation heating and thermoelectron generating electrode 2 includes a first conductor rod 2a, a second conductor rod 2b, and a plurality of third conductor rods 2c. Note that the plurality of third conductor rods 2c are heat generating parts, and the first conductor rods 2a and the second conductor rods 2b are fixed parts of the plurality of third conductor rods 2c.
The first conductor rod 2a and the second conductor rod 2b are arranged parallel to each other and parallel to the main surface 6a of the substrate holder 6. One end of the plurality of third conductor bars 2c is fixed to the first conductor bar 2a, and the other end is fixed to the second conductor bar 2b. The plurality of third conductor rods 2c are arranged parallel to each other at equal intervals.
As shown in FIG. 2, the first conductor rod 2a is fixed to a first leaf spring type tension applying means 3a, and the first leaf spring type tension applying means 3a is fixed to the first power supply rod 5a. It is fixed via the first connection jig 5aa. The first leaf spring type tension applying means 3a is made of a metal that is an electrical conductor and can withstand high temperatures, such as tungsten, tantalum, or an alloy containing tantalum.
The first conductor rod 2a has a circular cross-sectional shape, for example, and is made of a metal with a high melting point, such as tungsten (W), tantalum (Ta), or an alloy containing tantalum. As the diameter of the first conductor rod 2a, a round rod having appropriate rigidity, for example, 1 mm to 5 mm in diameter is selected. The length of the first conductor rod 2a is larger than the main surface 6a of the substrate holding table 6, for example, 160 mm to 170 mm, for example, 160 mm.
As shown in FIG. 2, the second conductor bar 2b is fixed to a second leaf spring type tension applying means 3b, and the second leaf spring type tension applying means 3b is fixed to the second power supply rod 5b. It is fixed via the second connection jig 5bb. The second leaf spring type tension applying means 3b is made of a metal that is an electrical conductor and can withstand high temperatures, such as tungsten, tantalum, or an alloy containing tantalum.
The second conductor rod 2b has a circular cross-sectional shape, for example, and is made of a metal with a high melting point, such as tungsten (W), tantalum (Ta), or an alloy containing tantalum. As the diameter of the second conductor rod 2b, a round rod having appropriate rigidity, for example, 1 mm to 5 mm in diameter is selected. The length of the second conductive rod 2b is set to be larger than the main surface 6a of the substrate holder 6, for example, from 160 mm to 170 mm, for example, 160 mm.
The third conductor rod 2c is made of tungsten (W, φ=4.5 eV), tantalum (Ta, φ=4.2 eV), or an alloy containing tantalum, which is a material with a low work function φ from the viewpoint of thermoelectron generation. It is formed. The cross-sectional shape of the third conductor rod 2c is circular or rectangular in consideration of electrical resistance and surface area. Note that the third conductor rod 2c is referred to as a heat generating section.
In the high frequency plasma CVD apparatus according to the first embodiment of the present invention, a circular shape is selected. For example, from a diameter of 0.1 mm to 1.0 mm, for example, 0.3 mm is selected.
Note that the reason for selecting a diameter of 0.1 mm to 1.0 mm is that, as described in Patent Document 3, for example, it has a proven track record as a hot filament CVD apparatus and is valid as general knowledge.
The length of the third conductor rod 2c is the same as that of the first conductor rod 2a and the second conductor rod 2b. For example, the length is 160 mm, which is the same as the length of the first conductor rod 2a and the second conductor rod 2b. The reason for this is to generate thermoelectrons and plasma in an area wider than the area of the substrate 9. The interval between adjacent third conductor rods 2c is 3 mm to 10 mm, for example, 5 mm. The reason for this is that appropriate intervals are used to control the temperature of the substrate 9, and for example, as described in Patent Document 3, there is a track record of hot filament CVD, and it is valid as general knowledge. This is because.

When the third conductor rod 2c is made of tantalum, the electrical resistance of the third conductor rod 2c (tantalum wire) approximately has the following value. Incidentally, the resistivity of tantalum wire is 61.5x10 ^-6 Ωcm at 1,200°C.
Resistance value of third conductor rod 2c (tantalum wire) (diameter: 0.3 mm, length 16 cm) R
= Resistivity (Ω・cm) x Length (cm)/Cross-sectional area (cm ² )
= ^61.5x10-6 (Ωcm)x16(cm) ^/0.7x10-3 ( ^cm2 )
=1.4Ω...(1)
The distance between the third conductor rod 2c and the substrate 6 is determined in consideration of the setting conditions of the substrate temperature. Here, the substrate temperature is set at about 700 to about 1,200°C, for example, 1,000°C, and the temperature of the third conductor rod 2c, which generates a large amount of thermoelectrons as described later, is maximized. In order to satisfy this requirement, the distance between the third conductor rod 2c and the substrate 6 is selected to be in the range of approximately 4 mm to approximately 40 mm. For example, let it be 5 mm.

As shown in FIG. 1, the high-frequency plasma generating electrode 13 includes a quartz window 19a that transmits infrared rays, a raw material gas inlet 7a that introduces raw material gas, and a large number of raw material gas ejection holes 13a that spout the raw material gas. Equipped with. The source gas inlet 7a is connected to the source gas supply pipe 7b via a pipe joint 15 made of an insulating material. The high-frequency plasma generating electrode 13 is fixed to the vacuum vessel 1 with a vacuum apparatus flange 18 made of an insulating material, and is electrically insulated from the vacuum vessel 1.
A supply source of a raw material gas (not shown) containing at least carbon-containing gas and hydrogen gas (H ₂ ) is arranged upstream of the raw material gas supply pipe 7b. The high-frequency plasma generation electrode 13 includes a power feeding point 27 that receives high-frequency power supplied from a high-frequency power source 10, which will be described later.
_The carbon-containing gases include methane ( _CH4 ), _{ethane (C2H6), propane (C3H8), ethylene (C2H4 ) , propylene ( C3H6} ), and acetylene ( _{C2H2 ) .} ) is a gas containing at least one selected from the following. From the point of view of forming high quality diamonds, it is preferable to choose from methane (CH ₄ ), ethane (C ₂ H ₆ ) and propane (C ₃ H ₈ ) with sp3 hybrid orbitals. Here, methane (CH ₄ ) is selected as the carbon-containing gas.
The quartz window 19a is used to measure the temperature of the substrate 9 in cooperation with the radiation thermometer 19. Note that the quartz window 19a for temperature measurement has a characteristic of transmitting infrared rays emitted by the substrate 9 and the first radiation heating electrode 2.
A large number of raw material gas ejection holes 13a are arranged. The diameter of the source gas ejection hole 13a is, for example, approximately 0.4 mm to approximately 1 mm, and the aperture ratio is, for example, approximately 30% to approximately 90%. By setting the diameter of the hole to 0.4 mm to 1 mm, the raw material gas can be ejected uniformly. By setting the aperture ratio to 30% to 90%, the surface of the substrate 9 can be seen through the quartz window 19a for temperature measurement, so the temperature of the substrate 9 can be measured using the radiation thermometer 19 through the quartz window 19a. I can do it. Further, the radiation thermometer 19 can measure not only the temperature of the substrate 9 but also the temperature of the plurality of third conductor bars 2c.

As shown in FIGS. 1 and 2, the DC power supply means for supplying DC power to the first radiation heating and thermionic generation electrode 2 includes a DC power supply 8, an ungrounded DC power supply line 8a, and a high-frequency A coil 16 for cutting off power, a grounded DC power supply line 8b, an electrically ungrounded first vacuum current introduction terminal 12a, and an electrically grounded second vacuum current introduction terminal 12b. , is provided. Note that the DC power supply 8 is a DC power supply of a constant power control type, and can be controlled so that constant power always flows even if the load condition changes.
The ungrounded output terminal of the DC power supply 8 is connected to the first vacuum current introduction terminal 12a via the ungrounded DC power supply line 8a and the coil 16. A grounded output terminal of the DC power supply 8 is connected to a second vacuum current introduction terminal 12b via a grounded DC power supply line 8b.
That is, the DC power supply circuit of the DC power supply 8 includes, in order from the output terminal of the DC power supply 8, an ungrounded DC power supply line 8a, a coil 16, a first vacuum current introduction terminal 12a, and a first power supply rod 5a. , the first leaf spring type tension applying means 3a, the first conductor rod 2a, the plurality of third conductor rods 2c, the second conductor rod 2b, the second leaf spring type tension applying means 3b, the second power supply It is formed by a loop connecting the rod 5b, the second vacuum current introduction terminal 12b, the grounded DC power supply line 8b, and the grounded output terminal of the DC power source 8.
The DC power supply 8 is of a constant power control type, and controls the temperature of the third conductor rod 2c, which is a component of the first radiation heating and thermionic generation electrode 2, to about 1,000 to about 2,500°C, for example. , 2,400°C and can be controlled to a constant temperature. The DC power supply 8 uses a commercially available device, for example, a constant power control type DC power supply with an output current: max. 30 A, an output voltage: max. 1 kV, and an output power: max. 30 kW.
The coil 16 has an inductance that blocks high-frequency power generated by a high-frequency power supply 10 (described later) from entering the DC power supply 8. Note that the inductance that matches the frequency of the high-frequency power can be adjusted by adjusting the number of turns of the coil, and the high-frequency power can be cut off.

As shown in FIG. 1, the high-frequency power supply means for supplying high-frequency power to the high-frequency plasma generation electrode 13 includes a high-frequency power supply 10, a coaxial cable 10a, an impedance matching device 11, and a high-frequency power line 11a. It includes a grounded third vacuum current introduction terminal 12c and a third power supply rod 5c. Furthermore, the high-frequency plasma generating electrode 13 includes a power feeding point 27 that receives high-frequency power supplied from the high-frequency power source 10 .
The ungrounded output terminal of the high frequency power supply 10 is connected to the third vacuum current introduction terminal 12c via the coaxial cable 10a, the impedance matching device 11, and the high frequency power line 11a. The impedance matching device 11 is designed to minimize the strength of the reflected wave of the high frequency power supplied from the high frequency power supply 10 reflected from the third vacuum current introduction terminal 12c side to the upstream side and returned. Impedance adjustment means built into the impedance matching device 11 can be adjusted. The third vacuum current introducing terminal 12c and the power feeding point 27 are connected by a third power feeding rod 5c.
That is, the high-frequency power supply circuit of the high-frequency power supply 10 includes, in order from the output terminal of the high-frequency power supply 10, a coaxial cable 10a, an impedance matching device 11, a high-frequency power line 11a, a third vacuum current introduction terminal 12c, and a third power supply rod. 5c, and a feeding point 27. Note that the grounded terminal of the high frequency power source 10 is electrically connected to the wall of the reaction vessel 1 and the radiation heating/thermionic generation electrode 2 (in electrical continuity with the wall of the reaction vessel 1).
A band-shaped conductor plate or a coaxial cable is used as the high-frequency power line 11a. Here, a strip-shaped conductor plate with low impedance is used.
When the output voltage of the high frequency power source 10 is applied to the feed point 27, an electric field is generated between the high frequency plasma generating electrode 13 and the wall of the reaction vessel 1, and an electric field is generated between the high frequency plasma generating electrode 13 and the first wall. An electric field is generated between the thermionic generation electrodes 2 which also serve as radiation heating. When the electric field reaches a value that satisfies the conditions for plasma generation, the high frequency plasma generating electrode 13 generates main plasma in the region sandwiched between the high frequency plasma generating electrode 13 and the substrate holding table 6. Note that a dielectric material (not shown) is placed in the space on the back side and side surface side of the high-frequency plasma generation electrode 13 to suppress the generation of plasma in the space. Choose from ~300MHz. For example, a 60 MHz power source is used. Note that the DC power supply 10 and the impedance matching device 11 to be described later are commercially available devices, for example, a high frequency power supply with a frequency of 60 MHz and a maximum output of 1 kW.
In plasma generation using a frequency in the VHF band, the direction of the electric field formed by the high-frequency plasma generation electrode 13 changes from positive to negative in an extremely short period of time, so electrons in the plasma are captured in the plasma region and This has the effect of increasing density. As a result, high-density plasma can be generated, and plasma with low electron temperature can be generated.

Next, the form of radiant heat and thermoelectrons generated when DC power is supplied from the above-mentioned DC power supply means to the first radiant heating/thermionic generation electrode 2 will be described.
In FIG. 1, the output of the DC power supply 8 is, for example, 500 W to 10 kW, for example, 5 kW, and is supplied to the first radiation heating and thermoelectron generating electrode 2. Then, the third conductor rod 2c, which is a constituent member of the first radiation heating and thermionic generation electrode 2, which is the heat generating part, becomes red hot, and as shown in FIG. Radiant energy (radiant heat including infrared rays, visible light, ultraviolet rays, etc.) 100 is emitted from the third conductor rod 2c of the generating electrode 2, and the substrate 9 is heated. However, in FIG. 3, the reference numeral 100 indicates radiant energy (radiant heat including infrared rays, visible light, ultraviolet rays, etc.) radiated from the third conductor rod 2c.
The radiant energy (radiant heat including infrared rays, visible light, ultraviolet rays, etc.) 100 radiated from the third conductive rod 2c, which is the heat generating part, is based on the Stefan-Boltzmann law, for example, as described in Non-Patent Document 5. It is expressed as That is, the radiant energy Es emitted from the third conductor rod 2c is expressed by the following equation (2).
Es ∝ ε・σ・T ⁴ (w/cm ² ) ... (2)
Here, ε is the emissivity, σ is the Stefan-Boltzmann constant, and T is the absolute temperature of the third conductive rod 2c.
The radiant energy Q incident on the substrate 9 is expressed by the following equation (3), for example, as described in Non-Patent Document 5.
Q ∝ Es・Ss・cosθ/d ² ...(3)
However, Es is the radiant energy radiated from the third conductor bar 2c, Ss is the surface area of the third conductor bar 2c, and θ is the third energy emitted from the third conductor bar 2c with respect to the normal line of the substrate 9 as shown in FIG. The angle (elevation angle) at which the conductor bar 2c is looked up, d is the distance between the third conductor bar 2c and the substrate 9.
Furthermore, exchange of radiant energy occurs between two adjacent high-temperature objects. For example, if the temperature of a first high-temperature object placed next to each other is _T1 and the temperature of a second high-temperature object is _T2 , the net energy exchange amount ΔE per unit area is expressed by the following equation (4). be done.
ΔE ∝ ε・σ・(T ₁ - T ₂ ) ⁴ ...(4)
This indicates that, if the temperatures are the same, no net energy exchange occurs between the plurality of third conductor rods 2c arranged next to each other. In other words, since the temperatures of the plurality of third conductor rods 2c arranged next to each other are almost the same, there is no net energy exchange between them.
The surface temperature of the substrate 9 is determined by the distance between a plurality of adjacent third conductor bars 2c and the distance between the third conductor bars 2c and the substrate 9, as expressed by the above formulas (2) to (4). d and the output of the DC power supply 8, while measuring the surface temperature of the substrate 9 with the radiation thermometer 19, the surface temperature of the substrate 9 is made to be almost uniform over the front surface of the substrate 9. , the distance between the plurality of third conductor rods 2c, the distance d between the third conductor rods 2c and the substrate 9, and the optimal values of the output of the DC power source 8 are determined in advance through experiments.
Here, the distance between the plurality of third conductor rods 2c, the distance between the third conductor rods 2c and the substrate 9, and the optimal values of the output of the DC power source 8 are determined in advance. The surface temperature is set and controlled at about 700 to about 1,200°C, for example 1,000°C.

On the other hand, when the third conductor rod 2c, which is a heat generating portion, is heated to a high temperature, thermoelectrons are generated. FIG. 3 schematically shows how thermionic electrons are generated. However, in FIG. 3, the reference numeral 101 is a thermoelectron emitted from the third conductor rod 2c.
When the third conductor rod 2c is at a high temperature, it generates thermoelectrons according to the Richardson-Dushman equation, for example, as described in Non-Patent Document 4.
That is, the number Ne of thermoelectrons generated by the third conductor rod 2c is expressed by the following equation (5).
Ne ∝ T ²・exp {-φ/kT} (Unit: A/m ² ) ...(5)
However, T is the absolute temperature of the third conductor rod 2c, φ is the work function of the third conductor rod 2c, and k is the Boltzmann constant.
Therefore, the higher the temperature of the third conductive rod 2c and the lower the work function, the greater the number of emitted thermoelectrons. For example, according to Non-Patent Document 4, the work function φ of tungsten (W) is 4.5 eV, the work function φ of tantalum (Ta) is 4.2 eV, and the thermionic emission characteristics of tungsten W (melting point: 3 ,000°C), 0.01 A/cm ² at 2000°C and 1 A/cm ² at 2,400°C are obtained, and for tantalum Ta (melting point: 2,850°C) at 1,400°C, 0.01 A/cm 2 is obtained. At 01 A/cm ² and 1,800° C., 1 A/cm ² has been obtained.
That is, the above equation (5) and the data described in Non-Patent Document 4 indicate that the higher the temperature of the third conductive rod 2c, the more thermoelectrons are generated. Furthermore, when compared in terms of their ability to generate thermoelectrons, it can be seen that tantalum is superior to tungsten.
Here, in order to maximize the amount of thermoelectrons generated, the temperature of the third conductive rod 2c is set to be below the melting point, and is selected to be the highest possible temperature. For example, while maintaining the surface temperature of the substrate 9 at a required value, the temperature of the third conductive rod 2c is set to as high as possible, for example, 2,400°C. However, since the temperature of the substrate 9 increases, the surface temperature of the substrate 9 is controlled to about 1,000° C. using a cooling means built into the substrate holding table 6.

Next, the form of plasma generated when high-frequency power is supplied from the above-mentioned high-frequency power supply means to the high-frequency plasma generation electrode 13 will be described below.
For example, a mixed gas of methane (CH ₄ ) and hydrogen (H ₂ ) is ejected from the raw material gas ejection hole 13a, the pressure is set to a predetermined value, and the output of the high frequency power source 10 is connected to the coaxial cable 10a and the impedance matching device. 11, it is supplied to the power feeding point 27 via the high frequency power line 11a and the third vacuum current introduction terminal 12c. Then, as shown in FIG. 3, plasma 102 is generated.
The plasma 102 is generated using a high frequency power source 10 whose frequency is in the VHF band (30 MHz to 300 MHz), and a first radiant heating and thermionic generation electrode 2 that generates thermionic electrons in the generation region of the plasma 102. Because of its location, it has the following characteristics.
(a-1): The third conductor rod 2c of the first radiation heating/thermionic generation electrode 2 generates thermoelectrons according to the Richardson-Dashman equation. The thermionic electrons 101 generated in the third conductor rod 2c of the first radiant heating and thermionic generation electrode 2 are generated by α action (electrons collide with gas molecules and are ionized, resulting in new Similar to the electrons generated by the action of (the action of generating electrons), the action of β action (the action of ions colliding with gas molecules and generating electrons), and the action of gamma (the action of positive ions colliding with the cathode and emitting electrons) It also has the effect of ionizing and dissociating gas molecules.
(b-1): Plasma is generated by an electric field formed by the high frequency power of the high frequency power supply 10 applied to the high frequency plasma generation electrode 13, but due to the presence of the thermoelectrons 101 (Edison effect), general plasma generation Compared to other conditions, high-frequency plasma is easily generated. That is, the thermoelectrons 101 are accelerated by an electric field of extremely high frequency, and VHF plasma is generated due to the α effect and β effect. In general plasma generation, it depends on Paschen's law (the discharge starting voltage Vs takes a minimum value at the product of the pressure p and the distance d between the electrodes: pd = 1 to 10 Pa・m), and under high pressure conditions It is difficult to generate a glow discharge. However, in the high frequency plasma CVD apparatus according to the first embodiment of the present invention shown in FIGS. Since the third conductor bar 2c of the thermionic electron generating electrode 2 contains thermionic electrons generated, the Edison effect and the super high frequency electric field application effect (the direction of the electric field changes between the positive direction and the negative direction in an extremely short period of time, The effect of increasing electron density as electrons are captured in the spatial region) makes it possible to generate plasma under high pressure conditions. As a result, high-frequency glow discharge plasma can be generated when the distance d between the electrodes is, for example, 5 mm to 10 mm and, for example, at several kPa to approximately 10 kPa.
(c-1): Since the frequency of the high-frequency power source 10 is in the VHF band (30MHz to 300MHz), there is an electron capture effect in the plasma space (electric field generation space), ion damage is suppressed, and high-density plasma is generated and maintained. Generation of high-density plasma with suppressed ion damage effectively promotes ionization and dissociation of gas molecules.
(d-1): When the plasma 102 is generated, a large amount of CH ₃ radicals (electrically neutral chemically active species), which are the main precursors in diamond formation, and a large amount of atomic H are generated. Ru. The CH ₃ radicals, as the main precursors for diamond formation, are chemically adsorbed onto the substrate surface and react surface chemically on the substrate surface to form a large number of C--C bonds. A large amount of atomic H is incident on the CH ₃ radicals chemically adsorbed on the substrate surface and the CC bonds formed by the CH ₃ radicals, and hydrogen components and By removing weakly bonded carbon components, a C--C bond with a regular tetrahedral structure (diamond structure) can be efficiently grown.

By the way, the transport (movement) of CH ₃ radicals in the gas phase follows Fick's law, which states that "the amount of diffusion of a substance per unit area and unit time is proportional to the concentration gradient." That is, this is expressed by the following equation (6). Note that the normal direction of the substrate surface is the coordinate x-axis, and the substrate surface is set to x=0. The amount of CH ₃ radicals flowing into the substrate surface per unit area and unit time J ₁ (CH ₃ ): (cm ⁻² · s ⁻¹ ) is determined by the diffusion coefficient of CH ₃ radicals being D(CH ₃ ).
J ₁ (CH ₃ )∝ D (CH ₃ )・{d[CH ₃ ]/dx} _x=0 ...(6)
However, {d[CH ₃ ]/dx} _x=0 is the CH ₃ concentration gradient (cm ⁻⁴ ) near the substrate surface.
The transport (movement) of atomic H follows Fick's law similarly to the transport (migration) of the CH ₃ radical described above. That is, the amount J ₂ (H) of atomic H flowing into the substrate surface is expressed by the following equation (7), where D(H) is the diffusion coefficient of atomic H.
J ₂ (H)∝ D(H)・{d[H]/dx} _x=0 ...(7)
However, {d[H]/dx} _x=0 is the H concentration gradient (cm ⁻⁴ ) near the substrate surface.
Note that the above equations (6) and (7) indicate that the transport amount of CH ₃ radicals and atomic H in the vicinity of the substrate surface increases as the respective concentrations increase.
Furthermore, in order to increase {d[CH ₃ ]/dx} _x=0 in the above formula (6), it is effective to increase the density of electrons in the plasma that generates CH ₃ radicals. are doing.
Furthermore, in order to increase {d[H]/dx} _x=0 in the above equation (7), it is effective to increase the density of electrons in the plasma that generates atomic H. ing.

In the high frequency plasma CVD apparatus according to the first embodiment of the present invention having the above characteristics (a-1) to (d-1), as shown in FIGS. 4 and 5, CH ₃ radicals and atomic H are It is thought that diamond is formed by the transport phenomenon of radicals mainly, the chemical reaction phenomenon on the substrate surface, and the action of pulling out hydrogen components and weakly bonded carbon components in the diamond formation precursor by a large amount of atoms. .
That is, in FIGS. 4 and 5, high concentration CH ₃ radicals generated in the region between the high frequency plasma generation electrode 13 and the substrate 9 move to the surface of the substrate 9 due to a diffusion phenomenon. A portion of it is chemically adsorbed onto the surface of the substrate 9. A portion of the CH ₃ radicals chemically adsorbed on the substrate surface are bonded in the form of CC due to a surface chemical reaction. Atomic H extracts H components and weakly bonded carbon components from the film surface and in the film. The extracted C and H components become gas and are discharged. On the substrate, C--C bonds are formed in a regular tetrahedral structure, and diamond grows.

Next, the operating procedure of the high frequency plasma CVD apparatus according to the first embodiment of the present invention will be explained with reference to FIGS. 1 to 5.
First, a substrate loading/unloading valve (not shown) of the reaction vessel 1 is opened, and the substrate 9 is placed on the main surface 6a of the substrate holding table 6. Next, after closing the substrate loading/unloading valve, the inside of the reaction vessel 1 is brought to a predetermined degree of vacuum via the exhaust port 17a and the exhaust port 7b using a vacuum pump (not shown).
Next, the output of the DC power supply 8 is supplied to the first radiation heating and thermionic generation electrode 2, and the surface temperature of the substrate 9 is set to, for example, 1,000°C based on the data known in advance. .
Next, while the surface of the substrate 9 is heated to the above temperature, the surface of the substrate 9 is cleaned using hydrogen plasma. Only hydrogen gas is introduced as the raw material gas from a raw material gas supply source (not shown), and the output of the high frequency power supply 10 is supplied to the high frequency plasma generation electrode 13 to generate hydrogen plasma. Note that the surface of the substrate 9 is cleaned using hydrogen plasma using a known method. The cleaning time of the surface of the substrate 9 with hydrogen plasma may be within several minutes. Here, the surface of the substrate 9 is cleaned using hydrogen plasma for 3 minutes, for example.
Next, the output of the high frequency power supply 10 is temporarily returned to zero.
Next, from the viewpoint of forming high-quality diamond, methane (CH ₄ ), ethane (C ₂ H ₆ ), and propane (C ₃ H ₈ ) having sp3 hybrid orbitals are used as raw material gases from a raw material gas source (not shown). Choose from. Here, for example, methane (CH ₄ ) is selected as the carbon-containing gas. The gas supply conditions include, for example, a flow rate ratio of hydrogen flow rate/methane gas flow rate = 100/3. Thereafter, methane gas and hydrogen gas whose predetermined flow rates are controlled by mass flow controllers for methane gas and hydrogen gas (not shown) are ejected from the raw material gas outlet 13a through the raw material gas supply port 7a from the raw material gas supply source (not shown). .
Next, the degree of opening and closing of the exhaust valve (not shown) is controlled by an exhaust valve control device (not shown), and the internal pressure of the reaction vessel 1 is maintained at approximately 1 kPa to approximately 10 kPa. Here, for example, it is set and maintained at 4 kPa.

Next, the frequency of the high frequency power source 10 is set to VHF band (30 MHz to 300 MHz), for example, 60 MHz, and the output is set to, for example, 200 W to 1 KW, here 500 W.
Then, as shown in FIG. 3, plasma 102 is generated between the high-frequency plasma generation electrode 13 and the substrate holding table 6. When the raw material gases methane (CH ₄ ) and hydrogen (H ₂ ) are turned into plasma, CH ₄ and H ₂ dissociate to generate CH ₃ radicals, atomic H, etc., which are precursors of diamond formation. The CH ₃ radicals, the atomic H, etc. diffuse and reach the surface of the substrate 9.

Next, since the thickness of the diamond film is proportional to the duration of generation of the plasma 102, the output of the high-frequency power source 10 is reduced to zero when a predetermined period of time has elapsed since the start of the output of the high-frequency power source 10. Also, the output of the DC power supply 8 is reduced to zero. The film forming time is determined based on data acquired in advance. Here, the duration is, for example, 30 minutes to 60 minutes, for example 60 minutes.
The film forming time depends on the distance between the high-frequency plasma generation electrode 13 and the substrate holder 6, the distance between the first radiation heating and thermionic generation electrode 2 and the substrate holder 6, the substrate temperature, the flow rate of methane gas, and the flow rate of hydrogen gas. , pressure, power, etc. can be grasped in advance and decisions can be made based on that data.
After the formation of the desired diamond film is completed, the supply of the methane gas and hydrogen gas is stopped, and the inside of the reaction vessel 1 is once evacuated to a high degree of vacuum. Thereafter, the reaction vessel 1 is returned to atmospheric conditions. After the reaction container 1 is returned to atmospheric conditions and the temperature of the substrate 9 reaches room temperature, a substrate loading/unloading valve (not shown) is opened and the substrate 9 is taken out. It is confirmed that a uniform diamond film is formed on the substrate 9 taken out from the reaction vessel 1.

As shown in the above description, in the high frequency plasma CVD apparatus according to the first embodiment of the present invention, the first radiation heating and thermoelectron generating electrode 2, the DC power supply 8, and the high frequency plasma generating electrode 13 , a high frequency power supply 10 with a frequency of 60 MHz, etc., it is possible to handle large area substrates, which is difficult with conventional devices.
That is, the high frequency plasma CVD apparatus according to the first embodiment of the present invention has the following characteristics.
(A-1): In the device configuration, it is a heat generating part made of tantalum, an alloy containing tantalum, or tungsten that emits radiant energy (radiant heat), generates thermoelectrons, and forms an ultra-high frequency electric field. A first radiant heating and thermoelectron generating electrode 2 equipped with a third conductor rod 2c, a DC power source 8 equipped with a coil that blocks the intrusion of high frequency power, a high frequency plasma generating electrode 13, and a high frequency power source 10. It is characterized by being used as a main component.
(Ro-1): The third conductor rod 2c of the first radiation heating and thermionic generation electrode 2, which is the heat generating part, is made of tantalum with a small work function φ, an alloy containing tantalum, or tungsten (the φ of tantalum is 4.2 eV, and tungsten's φ=4.5 eV), it has the effect of effectively generating thermal electrons as the temperature rises. In addition, the high-frequency plasma generation electrode 13 can effectively generate high-density plasma by a super-high-frequency electric field by supplying a super-high-frequency voltage in the VHF band (30 MHz to 300 MHz), and can synergize with the Edison effect of the thermoelectrons. This has the effect of making it possible to form ultra-high density plasma. Further, the first radiation heating/thermionic generation electrode 2 has the function of uniformly heating the substrate temperature to an arbitrary temperature selected from the range of about 800° C. to about 1,200° C.
(C-1): With the above (B-1), it becomes possible to turn the raw material gas, a mixed gas of methane and hydrogen, into plasma at high density and generate a large amount of CH ₃ radicals, atomic hydrogen H, etc. This has the effect that diamond can be efficiently formed on a substrate controlled at a high temperature. Since the wavelength of the high-frequency power that excites the high-density plasma is as long as a meter, it is necessary to control the substrate temperature and generate CH ₃ radicals, which is essential for forming large-area diamonds on 4- to 5-inch substrates. This makes it possible to control the production of high-concentration atomic hydrogen H, and to solve the problems faced by conventional diamond forming apparatuses.

(Second embodiment)
The high frequency plasma CVD apparatus according to the second embodiment of the present invention has the following structure in place of the first radiation heating and thermionic generation electrode 2 in the high frequency plasma CVD apparatus according to the first embodiment of the present invention described above. It is characterized in that the second radiation heating/thermionic generation electrode 22 shown in FIG.
A high frequency plasma CVD apparatus according to a second embodiment of the present invention will be described with reference to FIGS. 6(a) and (b). Reference is also made to FIGS. 1-5.
FIG. 6 is a schematic configuration diagram showing the configuration of the second radiation heating/thermionic generation electrode 22 which is a component of the high frequency plasma CVD apparatus according to the second embodiment of the present invention. FIG. 6(a) is a schematic configuration diagram of the second radiation heating and thermoelectron generating electrode 22, and FIG. 6(b) shows the first and second bar spring type tension applying means 3aa, 3bb and the fourth and It is a block diagram of the connection part of 5th current introduction terminal 21a, 21b for vacuum.
In FIG. 6(a), reference numeral 22 denotes a second radiation heating and thermoelectron generating electrode. The second radiation heating and thermoelectron generating electrode 22 is made of the same component as the first radiation heating and thermoelectron generating electrode 2, which is a component of the high frequency plasma CVD apparatus according to the first embodiment of the present invention. be done.
As shown in FIG. 6(a), the second radiation heating and thermoelectron generating electrode 22 includes a fourth conductor rod 2aa, a fifth conductor rod 2bb, and a plurality of sixth conductors which are heat generating parts. Equipped with a rod of 2ca. The fourth conductor bar 2 aa and the fifth conductor bar 2 bb are arranged parallel to each other and parallel to the main surface 6 a of the substrate holder 6 . One of the ends of the plurality of sixth conductor rods 2ca, which are heat generating parts, is fixed to the fourth conductor rod 2aa, and the other end is fixed to the fifth conductor rod 2bb. The plurality of sixth conductor rods 2ca are arranged parallel to each other at equal intervals.

As shown in FIG. 6(a), the fourth conductor rod 2aa has a rectangular cross-sectional shape, for example, and is made of a metal with a high melting point, such as tungsten (W), tantalum (Ta), or an alloy containing tantalum. be done. For the dimensions of the fourth conductor rod 2aa, select a square rod having appropriate rigidity, for example, cross-sectional dimensions of approximately 2 mm to 5 mm x 2 mm to 5 mm. The length of the fourth conductive rod 2aa is set to be larger than the main surface 6a of the substrate holding table 6, for example, 160 mm to 170 mm, for example, 160 mm.
Further, as shown in FIGS. 6(a) and 6(b), the fourth conductor rod 2aa is fixed to the first rod spring type tension applying means 3aa, and the fourth conductor rod 2aa is fixed to the first rod spring type tension applying means 3aa. is fixed to a power supply rod 5a of a third vacuum current introduction terminal 21a, which will be described later, via a third connection jig 20a. The first bar spring type tension applying means 3aa is made of a metal that is an electrical conductor and can withstand high temperatures, such as tungsten, tantalum, or an alloy containing tantalum.
As shown in FIG. 6(a), the fifth conductor rod 2bb has a rectangular cross-sectional shape, for example, and is made of a metal with a high melting point, such as tungsten (W), tantalum (Ta), or an alloy containing tantalum. be done. As for the dimensions of the fifth conductor rod 2bb, a square rod having appropriate rigidity, for example, a cross-sectional size of approximately 2 mm to 5 mm x 2 mm to 5 mm is selected. The length of the fifth conductive rod 2bb is set to be larger than the main surface 6a of the substrate holding table 6, for example, 160 mm to 170 mm, for example, 160 mm.
Further, the fifth conductor bar 2bb is fixed to the second bar spring type tension applying means 3bb as shown in FIGS. 6(a) and 6(b). The second bar spring type tension applying means 3bb is fixed to the power supply rod 5b (not shown) via a fourth connection jig 20b. The second bar spring type tension applying means 3bb is made of a metal that is an electrical conductor and can withstand high temperatures, such as tungsten, tantalum, or an alloy containing tantalum.
The sixth conductor rod 2ca, which is a heat generating part, is made of tungsten (W, φ=4.5eV), tantalum (Ta, φ=4.2eV), or tantalum, which is a material with a low work function φ from the viewpoint of thermoelectron generation. It is made of an alloy containing. The cross-sectional shape of the sixth conductor rod 2ca is circular or rectangular in consideration of electrical resistance and surface area. Here, choose a rectangle as shown below.

In the high-frequency plasma CVD apparatus according to the second embodiment of the present invention, a rectangular cross-sectional shape is selected as the sixth conductor rod 2ca.
For example, 0.1 mm in thickness x 0.706 mm in width is selected from 0.1 mm to 1.0 mm in thickness and 0.5 to 1 mm in width. The reason for choosing the thickness of 0.1 mm x width of 0.706 mm is that the electrical resistance value is approximately the same as that of the third conductor rod 2c (tantalum wire, diameter: 0.3 mm) of the high-frequency plasma CVD apparatus according to the first embodiment. In order to do so.
By the way, from the viewpoint of heating the substrate 9 and the number of thermoelectrons generated, if the heating elements of the first and second radiation heating and thermoelectron generating electrodes have the same cross-sectional area, they will be circular (for example, 0.3 mm in diameter). ) and a rectangle (for example, 0.1 mm thick x 0.706 mm wide), it is considered that the rectangle with a longer circumference is better because it has a larger surface area.

The electrical resistance of the sixth conductor rod 2ca, which is a heat generating portion, has a value roughly shown below. Incidentally, the resistivity of tantalum material is 61.5x10 ^-6 Ωcm at 1,200°C.
Resistance value of tantalum sixth conductor rod 2ca (thickness 0.1mm x width 0.706mm, length 16cm) R
= Resistivity (Ω・cm) x Length (cm)/Cross-sectional area (cm ² )
= ^61.5x10-6 (Ωcm)x16(cm) ^/0.7x10-3 ( ^cm2 )
=1.4Ω...(8)
The distance between the sixth conductor rod 2ca and the substrate 6 is determined in consideration of plasma generation conditions and substrate temperature setting conditions. Here, the substrate temperature is set at about 300 to about 600°C, for example, 500°C, and the temperature of the sixth conductor rod 2ca is maximized, which is a condition for increasing the generation of thermoelectrons, which will be described later. In order to satisfy the conditions that the generated plasma is in a glow discharge region, the distance between the sixth conductor rod 2ca and the substrate 6 is selected to be in the range of about 5 mm to about 40 mm. For example, let it be 8 mm.

Here, the sixth conductor rod 2ca which is a heat generating part used in the high frequency plasma CVD apparatus according to the second embodiment of the present invention, and the heat generating part used in the high frequency plasma CVD apparatus according to the first embodiment of the present invention. The thermionic generation ability of the third conductor rod 2c, which is the third conductor rod 2c, will be compared.
The number Ne of thermoelectrons generated by the sixth conductor rod 2ca and the third conductor rod 2c is determined by the Richardson-Dushman equation. That is, it is expressed by the following formula.
Ne ∝ T ²・exp {-φ/kT} (Unit: A/m ² ) ...(5)
However, T is the absolute temperature of the sixth conductor rod 2ca and the third conductor rod 2c, φ is the work function of the sixth conductor rod 2ca and the third conductor rod 2c, and k is the Boltzmann constant.
Since the above formula (5) is the number Ne of thermoelectrons generated per unit area, in the case of the sixth conductor rod 2ca, the surface area of the sixth conductor rod 2ca, that is, thickness 0.1 mm x width 0.706 mm. The number is proportional to the circumferential length of 1.612 mm.
On the other hand, in the case of the third conductor rod 2c, the number is proportional to the surface area of the third conductor rod 2c, that is, the circumferential length of a diameter of 0.3 mm = 0.942 mm.
That is, the sixth conductor rod 2ca has the same electrical resistance value as the third conductor rod 2c in the high-frequency plasma CVD apparatus according to the first embodiment of the present invention, but has a circumferential length similar to that of the third conductor rod 2c. The conductor rod 2c (diameter 0.3 mm) is 0.942 mm, while the sixth conductor rod 2ca (rectangular 0.1 mm x 0.706 mm) is 1.612 mm, which is approximately 1.7 times larger.
Under the same electrical resistance value, the circumference is approximately 1.7 times as large as that of the third conductor rod 2c, which means that the amount of thermoelectrons emitted from the sixth conductor rod 2ca is approximately 1.7 times that of the third conductor rod 2c. It means doubling.
Therefore, the high frequency plasma CVD apparatus according to the second embodiment of the present invention can increase the amount of thermoelectrons generated compared to the high frequency plasma CVD apparatus according to the first embodiment of the present invention, In order to strengthen the effect of increasing plasma density, a mixed gas of carbon-containing gas and hydrogen, which is the raw material gas, is turned into plasma at high density, and a large amount of CH ₃ radicals or C ₂ H ₃ radicals, etc. and atomic hydrogen H, etc. are generated. This makes it possible to efficiently form a carbon-based thin film on a substrate controlled at a high temperature.

Next, the operating procedure of the high frequency plasma CVD apparatus according to the second embodiment of the present invention will be explained with reference to FIGS. 1, 6, and 7. The following description will be made on the premise that the high-frequency plasma CVD apparatus according to the second embodiment of the present invention is applied to graphene formation, which is one application theme.
First, a substrate loading/unloading valve (not shown) of the reaction vessel 1 is opened, and the substrate 9 is placed on the main surface 6a of the substrate holding table 6. Next, after closing the substrate loading/unloading valve, the inside of the reaction vessel 1 is brought to a predetermined degree of vacuum via the exhaust port 17a and the exhaust port 7b using a vacuum pump (not shown).
Next, the output of the DC power supply 8 is supplied to the second radiation heating/thermionic generation electrode 22, and the surface temperature of the substrate 9 is set to, for example, 500° C. based on data known in advance.
Next, while the surface of the substrate 9 is heated to the above temperature, the surface of the substrate 9 is cleaned using hydrogen plasma. Only hydrogen gas is introduced as the raw material gas from a raw material gas supply source (not shown), and the output of the high frequency power supply 10 is supplied to the high frequency plasma generation electrode 13 to generate hydrogen plasma. Note that the surface of the substrate 9 is cleaned using hydrogen plasma using a known method. The cleaning time of the surface of the substrate 9 with hydrogen plasma may be within several minutes. Here, the surface of the substrate 9 is cleaned using hydrogen plasma for 3 minutes, for example.
Next, the output of the high frequency power supply 10 is temporarily returned to zero.
Next, from the viewpoint of forming high-quality graphene, ethylene (C ₂ H ₄ ), propylene (C ₃ H ₆ ), and acetylene (C ₂ H 6 ) having sp2 hybrid orbitals were used as raw material gases from a raw material gas supply source (not shown). ₂ ) Choose from etc. Here, for example, ethylene (C ₂ H ₄ ) is selected as the carbon-containing gas.
The gas supply conditions include, for example, a flow rate ratio of hydrogen flow rate/ethylene gas flow rate = 100/1. Thereafter, ethylene gas and hydrogen gas whose predetermined flow rates are controlled by mass flow controllers for ethylene gas and hydrogen gas (not shown) are supplied from a raw material gas supply source (not shown) to the raw material gas ejection hole 13a via the raw material gas supply port 7a. Make it squirt.
Next, the degree of opening and closing of the exhaust valve (not shown) is controlled by an exhaust valve control device (not shown), and the internal pressure of the reaction vessel 1 is maintained at approximately 133 Pa to approximately 1,333 Pa. In the field of microcrystalline silicon film formation using a plasma CVD apparatus, high pressure conditions of approximately 133 Pa or higher are well known as a means of suppressing ion damage. Here, for example, it is set and maintained at 133 Pa.

Next, the frequency of the high frequency power source 10 is set to VHF band (30 MHz to 300 MHz), for example, 60 MHz, and the output is set to, for example, 200 W to 1 KW, here 500 W.
Then, plasma 102 is generated between the high-frequency plasma generation electrode 13 and the substrate holding table 6. When the raw material gases ethylene (C ₂ H ₄ ) and hydrogen (H ₂ ) become plasma, C ₂ H ₄ and H ₂ dissociate to form C ₂ H ₃ radicals, etc., which are precursors of graphene formation, and atomic H, etc. occurs. The C ₂ H ₃ radicals, the atomic H, etc. diffuse and reach the surface of the substrate 9 . Note that C ₂ H ₃ radicals and the like and atomic H and the like diffuse and move in proportion to the concentration gradient according to Fick's law.
It is thought that the C ₂ H ₃ radicals that have moved from the plasma region to the surface of the substrate 9 are chemically adsorbed and spontaneously form graphene through a reaction on the substrate surface, as shown in FIG.
That is, in FIG. 7, highly concentrated C ₂ H ₃ radicals generated in the region between the high frequency plasma generation electrode 13 and the substrate 9 move to the surface of the substrate 9 due to a diffusion phenomenon. A portion of it is chemically adsorbed onto the surface of the substrate 9. A portion of the C ₂ H ₃ radicals chemically adsorbed on the substrate surface are bonded in the form of C—C due to a surface chemical reaction. It is thought that the C ₂ H ₃ radicals chemically adsorbed on the substrate surface react strongly on the substrate surface and preferentially form planar bonds. The atomic H that has moved from the plasma region to the surface of the substrate 9 extracts H components and weakly bonded carbon components from the film surface and in the film. The extracted C and H components become gas and are discharged. On the substrate, CC bonds are formed in the graphene structure to form graphene.
Note that Patent Document 1 describes data that graphene does not grow any further after several layers are formed.

Next, in graphene formation by plasma CVD, if the initial graphene nuclei are uniformly formed over the entire surface of the substrate 9 at a low density, the thickness automatically stops after a few layers. The film forming time is 1 minute to 20 minutes, for example, 5 minutes. That is, when 5 minutes have elapsed from the start of output supply from the high-frequency power source 10, the output is set to zero.
The film forming time depends on the distance between the high-frequency plasma generation electrode 13 and the substrate holder 6, the distance between the second radiation heating and thermionic generation electrode 22 and the substrate holder 6, the substrate temperature, the flow rate of ethylene gas, and the amount of hydrogen gas. Data related to the relationship between flow rate, pressure, power, etc. can be grasped in advance and decisions can be made based on that data.
After the desired graphene film formation is completed, the supply of the ethylene gas and hydrogen gas is stopped, and the inside of the reaction vessel 1 is once evacuated to a high degree of vacuum. Thereafter, the reaction vessel 1 is returned to atmospheric conditions. After the reaction container 1 is returned to atmospheric conditions and the temperature of the substrate 9 reaches room temperature, a substrate loading/unloading valve (not shown) is opened and the substrate 9 is taken out. It is confirmed that uniform graphene is formed on the substrate 9 taken out from the reaction vessel 1.

As shown in the above description, the high frequency plasma CVD apparatus according to the second embodiment of the present invention includes the second radiation heating and thermoelectron generating electrode 22, the high frequency plasma generating electrode 13, and the DC power source 8. , a high frequency power supply 10 with a frequency of 60 MHz, etc., it is possible to handle large area substrates, which is difficult with conventional devices.
That is, the high frequency plasma CVD apparatus according to the second embodiment of the present invention has the following characteristics.
(A-2): In the device configuration, a second thermionic-generating electrode 22 that emits radiant energy (radiant heat) and generates thermionic electrons and is made of tantalum, an alloy containing tantalum, or tungsten; It is characterized by using as main components a DC power supply 8 equipped with a coil that blocks the intrusion of high-frequency power, a high-frequency plasma generation electrode 13 that generates VHF plasma that suppresses ion damage, and a high-frequency power supply 10 with a frequency of 60 MHz. shall be.
(Ro-2): The second radiation heating and thermoelectron generating electrode 22 is made of tantalum, an alloy containing tantalum, or tungsten (φ = 4.2 eV for tantalum, φ = 4.5 eV for tungsten) with a small work function φ. Because of this formation, it has the effect of effectively generating thermoelectrons as the temperature rises. Furthermore, the high-frequency plasma generation electrode 13 is capable of effectively generating high-density plasma using a super-high-frequency electric field when supplied with a super-high-frequency voltage in the VHF band (30 MHz to 300 MHz), and is capable of generating high-density plasma using the second radiation heating and thermionic Due to the synergistic effect of the thermoelectrons emitted from the generation electrode 22 and the Edison effect, an ultra-high density plasma can be formed. Further, the second radiation heating/thermionic generation electrode 22 has the function of uniformly heating the substrate temperature to an arbitrary temperature selected from the range of about 300° C. to about 600° C.
(C-2): By the above (B-2), it is possible to turn the mixed gas of ethylene and hydrogen, which is the raw material gas, into plasma at high density and generate a large amount of C ₂ H ₃ radicals etc. and atomic hydrogen H etc. This makes it possible to efficiently form graphene on a substrate controlled at a high temperature. Since the wavelength of the high-frequency power that excites the high-density plasma is as long as meter-level, it is necessary to control the substrate temperature and generate C ₂ H ₃ radicals, which is essential for forming large-area graphene on 4-inch to 5-inch substrates. It is possible to control the generation of atomic hydrogen H, etc., and to control the generation of high-concentration atomic hydrogen H, which has the effect of solving the problems faced by conventional graphene-based devices.

1... reaction container,
2...first radiation heating and thermionic generation electrode,
2a... first conductor rod,
2b... second conductor rod,
2c... A plurality of third conductor rods which are heat generating parts,
3a, 3b...first and second leaf spring type tension applying means,
3aa, 3bb...first and second bar spring type tension applying means,
6... Board holding stand,
6a...Main surface of substrate holding stand,
7a... Raw material gas supply port,
8...DC power supply,
9...Substrate,
10...High frequency power supply,
11... Impedance matching box,
12a, 12b, 12c...first, second and third vacuum current introduction terminals,
13...High frequency plasma generation electrode,
13a... Raw material gas ejection hole,
15...Pipe joint made of insulating material,
16...Coil,
18... Flange for vacuum equipment formed of insulating material,
19... Radiation thermometer,
19a...Quartz window for temperature measurement,
22...Second radiation heating and thermionic generation electrode,
27...Power supply point.

Claims (2)

a reaction vessel equipped with a supply system and an exhaust system for a source gas containing at least carbon-containing gas and hydrogen gas (H ₂ ), and a main surface disposed inside the reaction vessel to hold a substrate, and the substrate a substrate holder equipped with a substrate cooling means using a refrigerant to control the temperature of the substrate; and a radiant heating and thermionic generation electrode disposed opposite to the main surface of the substrate holder to generate radiant heat and thermoelectrons. , a DC power source that supplies DC power to the radiant heating/thermionic generation electrode, a high frequency plasma generating electrode that is disposed opposite to the radiant heating/thermionic generating electrode and converts the raw material gas into plasma, and the high frequency plasma. A high-frequency plasma CVD apparatus comprising a high-frequency power source that supplies high-frequency power to a generating electrode via an impedance matching device,
The heat generating part of the thermionic generation electrode that also serves as radiation heating is formed of tungsten, tantalum, or an alloy containing tantalum, which is a material with a low work function φ,
The high frequency power supply generates power at a frequency selected from the VHF band (30MHz to 300MHz),
The high-frequency plasma generation electrode is formed into a box shape having a cavity inside using a metal material, and the box-shaped high frequency plasma generation electrode is fixed to the wall of the reaction container by penetrating through an electrical insulating material. A surface of the box-shaped high-frequency plasma generation electrode that does not face the radiant heating/thermionic generation electrode is provided with a power feeding point to which the power of the high-frequency power supply is supplied and an inlet for the raw material gas, and the box-shaped high-frequency plasma is generated. A quartz window that transmits infrared rays is arranged on the surface of the generation electrode in contact with the atmosphere, and a quartz window with a diameter of 0.3 mm to 1.0 mm is disposed on the surface of the box-shaped high frequency plasma generation electrode facing the radiant heating and thermionic generation electrode. A large number of injection holes for the raw material gas with an aperture ratio of 30% to 90% are arranged, and the radiation thermometer placed outside the reaction vessel is used to measure the temperature of the raw material gas through the quartz window and the injection holes for the raw material gas. A high frequency plasma CVD apparatus characterized in that the temperature of the substrate and the temperature of the thermionic generation electrode that also serves as radiation heating are measured. _The carbon-containing gases include methane ( _CH4 ), _{ethane (C2H6), propane (C3H8), ethylene (C2H4 ) , propylene ( C3H6} ), and acetylene ( _{C2H2 ) .} 2. The high-frequency plasma CVD apparatus according to claim 1, wherein the gas contains at least one selected from the following.

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